Transmission of pictures by electricity



July14,1925. 1,545,708

' D. M. TERRY TRANSMISSION OF `PICTURES BY ELECTRICITY Fvilduay s. 1924 Patented July 14, 1925.

.UNITED STATES PATENT ori-ica- 4:DONALD M. TERRY, OF NEW YORK, N. Y., ASSIGNOB TO WESTERN ELECTRIC' COM- PANY, INCORPORATED, OF NEW YORK, N. Y., A. CORPORATION OF NEW YORK.

TRANSMISSION OF PICTURES BY ELECTRICITY.

i Application led Hay 8,

New York and State of New York, have= linvented certain new and. useful Improvements in Transmission of Pictures by Elect-ricity, of which the following is a full, clear, concise, and exact description.

This invention relates to the transmission of pictures by electricity and more particularly to means for controlling the reproducing process. Y

In the transmission of pictures by electricity by means of. sendingl and reproducing drums and intermediate transmission equipment, it is not only necessary -to drive the drums in exact synchronism but it isequally important to start them simultaneously.A One arrangement for accomplishing this result in a sim le manner is disclosed in a copending ap`p ication of M. B. Long, Serial No. 681,347, filed December18, 1923. In the Long arrangement, the light valve is operated by demodulated current from an electron discharge demodulator and the same current is Iused to energize the control apparatus. As disclosed in 'a copendin app ication of E. C. Wente, Serial No. 01,016, filed March 22, 1924, an improved reproducing arrangement comprises a light valve upon which the modulated carrier Wave is directly impressed and which functions itself as a demodulator. When such a light valve is employed, the Long vcontrol arrangement is not suitable.

The object of this invention is to accom-` plish the control of the drums in a picture transmission system of the type disclosedl in the Wente application supra in a simple and effective manner.

According to one embodiment of theinvention, the last discharge device at the reproducing terminal functions as an amplifier to impress modulated carrier current on. the light Valve for -picture lreproduction and asy a detector to control the release mechanism of the reproducing 'drum for starting the process of reproduction. The changeover is effected by remote control of the carrier current at the sending terminal.

The novel features which are considered characteristic of this invention are set forth with particularity in the appended claims. The invention, both as to its organiaat-ion 1924. Serial No. 711,748.

vthis invention, showing the control apparatu's.

Fig. 2 is a schematic circuit arrangement of reproducing terminal equipment also showing the control apparatus.

Fig. 3 is a schematic fragmentary sketch showing the drum detent arrangement.

At the transmitting terminala sending drum 5 1s rot-ated and moved axially at the same time by the rotation of shaft 6. The

shaft 6 is driven by means .of friction drive .I. At the reproducing terminal, reproducmg drum 501s similarly rotated and moved axially by the rotation of shaft 51 which isl driven. by friction drive 52. Both shafts may be rotated in either direction by, individual reversible motors (not shown). A suitable driving and synchronizing system is disclosed in the Long application supra.

Referring now to Fig. 1, a transparency 8 of the picture to be transmitted is mounted on the sending drum 5. vLight from source 9 is concentrated by means of lens 10, upon a small area of the transparency 8. Light from source 9 passesA through the transparency 8 and the transparent drum 5 into photo electric cell P, where it determines the amount of current flowing 4from battery 11 and consequently the otential impressed upon the input circuit o -picture amplifier PA. Current from a source of carrier wave C is impressed upon a modulator M by way of conductor 12, contact 13 tector RA-D is connected through conductor 54, contact 55 of relay 53, and conductor 56' to one terminal of the primary winding this winding is connected through conductor 58, to thepositive terminal of plate battery 61. The other terminal of battery 61 is connected to the cathodes of the electron discharge devices' and to ground. The secondary winding of transformer 57 is direct-ly connected to string 62 of light valve V. The vibration of strin 62 controls the exposure. of a light sensitive record blank 63 mounted on reproducing drum by light from source 64 through lenses 65 and 66.

Forthe transmission of a icture line L of Fig. 1 is associated with 1ne L of Fig. 2 through a circuit which is capable of transinitting voicefrequency currents. This connection may be through an ordinary telephone line, a carrier telephone channel o a radio telephone' channel. In thecircuit as shown, it is assumed that a picture is in `the process of being trans' mitted. The motors driving shafts 6 and 51 are rotating in such a direction as to cause axial motion ofthe drums 5 and 50 infthe direction indicated by the arrows. 'lhcrotation oi drum 5 lwith its vtransparencyjvg'pf the picture 'to vbe transmitted,

causes-the carrier wave from source' C to be modulated with ithe picture l characteristics inv modulator As the drum '5- moves in the direction .of the arrow, it will eventually enga estop ingfkey 18,`closingv a contact whi'chcompetes a vcircuit through battery 19, relay '20a'nd `right hand contact of stop- .ping`.sw itchj21. `The len'ergization of` relay 20,'atti'actsl/its armature- 22 which engages with a notch in detent disc 23 to stop the rotation'of shaft 6. The armature A22 is-normallyfheld in retractedfposition by' -spring .he shape of the 23 is clearl shown 1n Fig. 3. From that ligure, it is clear that the armaturel 22 whenin at tracted position willprevent the rotation f' of..shaft l6` in either direction. :Simultaneously with the closing of sto ping'key 18 at the transmitting terminal,t e reproducing drum 50' will engage stopping key 167 at the re rod-ucing terminal. The .closure of key 6 l through battery 68, relay 69 and-left hand will complete a circuit "e contact of stopping switch 70. T lifeenergization ,of relay 69 .attracts its armature 71.,

causing its engagement with dise-72` to.stop' l the `rotation of `shaft 51.

is'fnormally heldin `retracted position by spring.;73. The action of armature 71 in y .matically stopped.

serving as a detent ford'isc7 2 willbe'. clear from afreference to Fig. 3' and the previous I rodu'cingidrum 5 0 anddeveloped in well i5- ownf` m'anner. l f L Thevarmature 711 rocess is thus auto e light' sensitlve' rec- Starting key S is thrown to the left in which position contacts 13 and 16 are opened and contacts 25 and 26 are closed. The closure of contact 25 completes a circuit ifor relay 20 independently of the contacts of stopping key 18 and the right hand -contact of stopping switch 21. The closure of contact 26 completes a circuit for carrier waves from source C to line L independently of the'modulator M by way of conductor 27, contact 28 of test switch T,I

contact 26 of switch S, and conductor 17.

Stopping switch 21 is then closed in its left hand position.

vAs the circuits now stand relay 20 is energized through contact 25 and shaft 6 is preventedfrom rotating. Carrier current 1s outgoing `on the line L independently of the modulator M.

At therepro'ducing terminal of Fig. 2, another lightjsensitlve Vrecord blank is placed on reproducing drum 50;" stopping switch 70, thrown to its right hand'position'; and holding`v switch 75 is closed. Under these conditions', rela 69 is'energized by a circuitcompletedat olding switch 75 and shaft 51'is l'prevented from rotating by detent 71. Startingswitch 74 which is pref- 'erably a nonlocking key, is closed long enough to Yenergize rela 53, over a circuit including resistance 76, attery'61 and conductor 60. r.

i The energization of relay 53 converts the receiving amplifier-detector RAD from an amplifier to a. detector by substituting negative grid polarizing battery 79 of 40 volts in glace of battery 17 of 9 volts potential.

attery 7-9 isconnected inl series with 'the whole of resistance 81 at contact 8 0 vof relay ,53, before battery 77 isdisconnected from the upper part ofv resistance 81 at contact 59 of relay 53.v The upper part of resistance 81 has preferably a resistance of 7500 ohms and the lower part, 200,000 ohms. During the change-over,therefore, batteries 77 and 7 9fare connected in opposing relationship in series with 200,000 ohms, so thatno excessive-currents are present. 'lhe grid circuit of. the ampl ifer-.de tector R-A-D is'thu's never withoutla" negative'. polarizing potential and large surges of plate current 'are thus not present during the change-over, as would be'the case were the battery 77 dis connected from the grid before the battery 79 was applied thereto or viceversa. Were such surge not obviated,special precautions lwould need to be taken to insure that the .lightvalve V was first disconnected, otherrelay 82 by 86 independently of starting key 74. As

soon as starting key S (at. the sending ter-- minal) is thrownto its left hand position and the startin key 74 (at the reproducing terminal) has een closed to energize relay v 53,'holding key 75 at the4 reproducing terminal may be opened. The system is now in condition to start the transmission of another picture. The driving motors, if not already rotating, are'started in -such a di- .rection as tocause the drums5 and 50 to move in a dlrection opposite to that indicated by the arrows.

To' start the operation, the starting key S isfirst thrown to normal position in which condition each of the contacts 13, 16, 25 and 26 is open. The opening of contact 25, de-

energizes relay 20 and releases shaft 6. The opening 'of contact 26 interrupts the flow of carrier waves to the line-L. At contacts 13 and 16, the input and output circuits of the modulatorare interrupted. At the reproducing terminal the interruption of incoming carrier waves releases relay 82 and opens contacts 85 and 86 thereof. The opening of' contact 85, deenergizes magnet 69 and releases shaft 51. The opening of contact 86 deenergizes relay 53' and converts the receiving amplifier-detector'RA-D from a detector to an amplifier by substituting battery 77 for battery 79.

Starting switch S is then thrown to its right hand position and thel process of transmitting the picture continues in the manner hereinbefore described. When the picture surface has been traversed, drum 5 engages stopping key 29 and drum 50 engages p stopping key 87 to automatically ystop the drums 1n a manner similar to that described in connection with stopping keys 18 and 67.

To'transmit another picture, the process is repeated except that the direction of rotation of the driving motors is such that the drums 5 and 50 move again in the direction indicated by the arrows.

Condenser 88 is provided to improve the detecting action of the receivingrv amplifierdetector RA-D. The resistance capacity networks'89 and 90, connected respectively -in'shunt of contacts 85 and 86, are provided to obviate sparking disturbances when these contacts arel opened at the start of the transmission process.

An' effective control arrangement is thus provided which operates with the drums moving in Veither direction. The last tube actsas an amplifier for picture transmission andas a detector for starting the transmission process. The starting of the reproducvpurpose disclosed in the Long application supra.

Various bodiment of the invention which has been describedi may be made without departing from the scope of the invention as defined in the appendedclaims. y

What I, claim is:

1. In asystem for the transmission of pictures by electricity comprising terminal .stations and apparatus at each station for the -transmission of pictures, the method which compries normallyl transmitting carrier Waves from one station to the other, detecting said carrier waves at one station to delay the transmitting process, interrupting the transmission of carrier waves `from the second station to start the picture transmission-process at the first station, simultaneously ,starting the picture transmitting process at the second station, and amplifying the carrier waves at the first station where before they Were detected.

2. In a system for recording intelligence, a movable record blank, a source of carrier waves modulated with the characteristics cf the intelligence to he recorded. an amplifier for amplifying carrier waves from said source, -means to record said intelligence from said amplified waves, and means to convert said amplifier into a detector to control the movement of said movable record blank.

3. Ina system for reproducing pictures from electricity, a movable light sensitive record blank, a source of carrier Waves modulated with the characteristics of the picture to be reproduced, an optical arrange- ,ment for exposing said record blank to remodifications of the specific emlll) from electricity, a reproducing drum, mcans to rotate said drum, a light sensitive record -blank mounted on said drum, a source of carrier waves modulated with the characteristics of the picture to be reproduced,v an electro-magnetic) light valve and optical arrange-j ment for exposing said record blank, an a m plifier for amplifying modulated carrier Waves from said carrier source andV impressing the amplified Waves upon said light valve, and switching means to convert said amplifier into a detector to control the rotation of said drum. I

5. In a system for the transmission of pictures by electricity, a reproducing drum, a light sensitive record blank mounted on said drum, means to rotate said drum, a source of carrier Waves modulated-With the characteristics of the picture to be reproduced, an amplifier for amplifying carrier Waves from said source, means to expose said. record blank in accordance with demo'dulated cur'- rent from said amplified waves, means tov prevent the rotation of said drum, a relay arranged when energized to cause said` means including a movable element for reproducing the picture, means to detect the carrier waves from said source to control the movement of said movable element, and

-means to convert said detecting means to amplifying means to amplify the modified carrier Waves for ,energizing said reproducing means.

7. In a system for transmitting pictures by electricity, a source of carrier waves, means including a movable element for modifying carrier waves from said source in accordance with the elements of a picture to be successively transmitted, restraining means to prevent the movement of said movable element, means including a secon'd movable element for reproducing the picture, a second restraining means to prevent the movement of said second movable element, means to detect carrier Waves from said source to control said second restraining means, means to convert said detecting means to amplifying means to amplify the modified carrier waves for energizing said reproducing means, and starting means to control both said first rest-raining means and carrier waves from said source.

8. Ina systeln for the transmission of pictures by electricity, a source of carrier waves, means including a movable-clement to modify carrier waves from said source in accordance with the elements of the picture to be successively transmitted, means including a second movable element for reproducing the picture, separate restraining means to prevent the movement of said movable elements, means to detect carrier waves Lerares from said source to control one of said re straining means, means to convert said detecting means to amplifying means to arm'y tures by electricity, a source of carrier waves, `means to modlfy carrier 'Waves from said source in accordance with the elements of a picture to be successively transmitted, means including a movable element for reproducing the picture, means to detect carrier Waves from said source to control the movement of said movable element, means to convert said detecting means to amplifying. means to amplify the modified carrier waves for energizing said reproducing means, said converting means including means to pre- A vent reconverting said amplifying means to detecting means by subsequent changes' in the character of the carrier Waves.

10. In a system for the transmission of' pictures by electricity, a circuit over which carrier Waves are received, a reproducing drum, a light valve, an electron discharge detector, means to lock saidreproducing' icc drum, 'a light valve, an electron discharge. i

detector, means to lock said reproducing drum in response to the receipt of carrier Waves by said detector," means to unlock said drum due to .an interruption inthe receipt of carrier waves and simultaneously to convert said electron discharge detector into an electron 'discharge amplifier, and means to' prevent a subsequent locking'of said repro ducing drum when carrier wavesare againv received.

12. In a system for the transmission of carrier waves are received, a reproducing' drum, a light valve, an electron discharge detector, a relay circuit. for locking the reproducing drum, and a second relay energized 'by current from said detector andl pictures by electricity, a circuit over which/.

adapted when carrier current is being received to cause the relay locking circut'to lock the drum and further adapted when carrier current is interrupted to unlock the drumand to simultaneously convert the detector into an amplifier.-

13. ln a system vfor the transmission' ofvpictures by electricity, a circuit overvwhich carrier waves are received, a reproducing fle drum, a light valve, an electron discharge detector, a relay circuit for locking the re- Aproducing drum, a second relay energized 'drum and urt er adapted when carrier current is interrupted to unlock the drum and to simultaneousl convert the detector into an amplifier, an a third relay controlled by said second relay for converting said detector into an amplifier and open-circuiting the energizing winding of the second relay so that it will not be energized when carrier waves are again received. l

14. ln av system for the transmission of pictures by electricity, a transmission circuit,"'"'a source of voice frequency carrier waves of one frequency, a. sending drum, a 'transparency of the picture mounted on said drum, a photo-electric cell within said drum, an amplifier for amplifying picture currents flowing throu h said photo-electric cell anelectron disc iarge modulator to modulate said carrier waves in accordance with said amplified picture currents and to impress modulated waves upon said trans mission circuit, a reproducing drum, a light valve, an electron discharge detectorv actuated by carrier current from saidtransmission circuit, a circuit including means for locking said sending drum in stationary position and for connecting said source to said transmission circuit, either inde ndently of or through said modulator an -for 'disconnectmg said source-from said transmission circuit, means to lock said reproducing drum 1n res onse to detected carrier waves received in ependentl of said modulator, means to unlock said rum due to interruptions in the received carrier waves and to simultaneously convert said detectorinto an amplifier for actuating said light valve toreproduce the icture, and means to prevent a subse uent ocking of' said reproducing drum w en carrier waves are again. received. y

1,5. In a system for the transmission of pictures by electricity,'a circuit over which carrier waves are received, a reproducing drum, la light valve,a three-electrode electron discharge detector, a source of negative polarizing potential for said detector, a rela circuit tovcontrol the rotation of the repro ucing drum, a second .relay adapted to connect a source of lower negative polarizing potential to said detector before disconnecting said first mentioned source, and.

a third relay energized by current from said detector and adapted when current is being received to cause the relay drum control cir-i cuit to cause the drum to remain stationary and further adapted when carrier .current is interrupted to cause rotation -of the drum and to simultaneously control said second relay to effect the substitution of vsaid lower potential source for said h iglier to .convert said detector into an amplifier. f

In witness whereof, I hereunto subscribemy name this 29th day of April A. D., 1924.

DONALUM, TERRY. 

